The invention relates to a pressure vessel for the storage of a compressed fluid, for example a compressed gas.
It often is desirable to integrate means for the control of the compressed fluid into a pressure vessel. For example, the safety of such a gas vessel can be increased considerably by fitting a solenoid operated shut-off valve into the vessel. The U.S. Pat. No. 5,562,117 describes such a shut-off valve that can be screwed into a CNG (Compressed Natural Gas) pressure-vessel used for CNG-vehicles. By means of such a valve, the supply of natural gas can be allowed or barred according to the needs of the engine. In addition, it is designed to remain fail-safe closed even if, in case of an impact, the part of the valve protruding from the neck of the pressure-vessel is shorn of, thereby possibly preventing a hazardous exit of gas.
It can also be of advantage to mount a unit for the control of the pressure of a compressed gas directly at the pressure vessel. Thus, the U.S. Pat. No. 6,041,762 describes a control module which is likewise mounted onto the CNG-vessel of a CNG vehicle. This module comprises a pressure-reducing valve which extends from the module into the pressure vessel, and serves for reducing the gas storing pressure down to the system-pressure required by the combustion engine. Due to this set-up, with the pressure-reducing means located at the gas tank, the high-pressure piping with its enormous weight, that connects the gas tank to the engine of the vehicle and increases the risk of leakage, can be omitted. In addition, an externally mounted part of the module is equipped with a solenoid-actuated shut-off valve for the cut-off of the gas flow as well as a check-valve to enable the filling of the tank, these units constituting further control means.
For vehicles powered by fuel that is stored in high-pressure vessels it is of advantage if the complete high-pressure part of the supply system to the engine is integrated into the vessel. It is thereby possible to easily remove the pressure vessel for external re-filling, as described in DE 195 39 329 A.
Generally, means for the control of compressed fluidsxe2x80x94wherein the control can also be a part of a closed-loop controlxe2x80x94such as pressure regulation, power regulation etc.xe2x80x94comprise all of the following: shut-off valves for the cut-off of the supply of the fluid to the consumer, pressure-reducing valves for controlling the pressure of the fluid, through-flow control valves that cut-off the supply of the fluid in case of excessive flow-out, e.g. in case of a leak in the piping, fusible-cut outs which are to enable a non-dangerous, controlled exit of the fluid in case of the external temperature exceeding a specific value, residual-pressure control valves preventing a complete purging of the vessel, as well as check valves to enable the filling of the pressure vessel.
It is state of the art to restrain compressed fluids like gases pressurized in vessels made of steal, or anyhow in vessels which completely consist of metal. There are also composite pressure vessels, as, for example, described in EP 0 753 700. These pressure vessels consist of a liner made of plastic or a light metal like aluminum and a layer reinforcing the liner and being realized by a winding of a fibre composite material. The reinforcement is realized by winding a fibre-composite around the liner, typical fibre materials being, for example, carbon fibres, aramid fibres, glas fibres, boron fibres or aluminum-oxide fibres or mixtures thereof, embedded in a duromer like epoxy resin or phenol resin, or in a thermoplastic like polypropylene etc. Compared to steel vessels, a considerable reduction in weight is possible.
It is known that for the manufacturing of such composite pressure vessels, neck portions are used that encapsulate the pressure vessel in the direction of the longitudinal axis and which are equipped with threads that are used for fitting valves onto the pressure vessel. These neck portions usually have a sleeve which connects to the liner on one side and which is wrapped around by the windings of the fibre reinforcement on the other side so that a leak-tight connection is effected, as described e.g. in DE 197 51 411. Such pressure vessels are usually used for vessel pressures up to 300 bar (4350 psi).
The invention is to integrate the units required for the control of a compressed fluid like a diaphragm controlled pressure-reducing valve, a shut-off valve, a through-flow controlling valve, a fusible cut-out, a residual-pressure valve or a fill valve or different combinations thereof into a pressure vessel. This allows for a high level of safety against mechanical damage as no parts of the valves extrude from the pressure vessel except those required for biasing the pressure-reducing diaphragm. Preferably the combined unit of control means and vessel should be constructed to be of low weight.
According to the invention, this problem is solved by a pressure vessel for the storage of a compressed gas with a closed vessel housing consisting of an essentially cylindrical body with pole-caps on both ends and with integrated control means for the release of the gas, including a pressure-reducing means heaving a high-pressure unit and a low-pressure unit and a controlled gas outlet, which pressure vessel is characterized in that at least one of the pole-caps is an element mounted to the cylindrical body and the majority of the components of the control means are mounted to this element and extend into the interior of the vessel housing; the components necessary for the control thus lie within the pressure vessel wall.
Preferred embodiments of the invention are to be found in the respective sub-claims.
The control means included in the pressure vessel in this way are, as already mentioned above, shut-off valves, pressure-reducing valves, preferably diaphragm controlled, through-flow control valves, fusible cut-outs, residual-pressure valves or fill-valves or of any optional combination of these.
An integrated shut-off valve can be operated either manually, or by solenoid or pneumatically. Should one of the latter two methods of operation be adopted, a manual override is incorporated to allow for opening or closing the valve even in case of interruption of the solenoid or pneumatical actuation.
Diaphragm-controlled pressure-reducing valves can work either spring- or dome-loaded. In the first case, the bias load required on the pressure-reduce diaphragm is achieved by a compressed spring placed in a spring housing and executing a force onto the membrane. Via a set screw that varies the spring tension, the bias tension and thus the outlet pressure of the pressure reducing valve required are set. In the second case, biasing is effected by a compressed pneumatic auxiliary fluid which is contained in a housing, the dome, above the diaphragm. By varying the pressure of the auxiliary fluid, the bias tension and thus the outlet pressure can be adjusted.
A residual-pressure valve is a check valve that is placed at the entry of the control components in the vessel. It closes if the storage pressure in the vessel drops under a specified value. This prevents the complete purging of the vessel. The residual-pressure valve can be equipped with a fine filter element to protect the control components.
According to the invention, the control means are surrounded by the wall of the vessel, and the wall of the vessel or a part thereof is shaped so that its material fulfills the function of specific control components such as, for example, the function of component housing walls, or that specific parts of the control means extruding from the vessel wall make up an inseparable unit with the vessel wall material.
With metallic vessels, this is realized by fitting a metal cap with the required bores and welding it to housing parts into which the respective components of the control means are to be built. They are designed in such a way that, upon finishing the production of the vessel, no components of the control means protrude from the outside face of the vessel with the exception of those components required to bias the pressure reducing diaphragm, i.e. the spring housing or dome, according to the version used. Subsequently, the cap is welded onto the cylindrical part of the vessel. Preferably, however, the pressure vessel according to the invention is manufactured by the manufacturing method for composite pressure vessels. Here, the aforementioned neck portions are replaced by pole-caps into which the components of the control means are built.
Further details, advantages and improvements of the invention will become apparent from the following description of preferred embodiments of the invention, referring to the drawings in which: